Jump to content

  • Log In with Google      Sign In   
  • Create Account


We have 4 x Pro Licences (valued at $59 each) for 2d modular animation software Spriter to give away in this Thursday's GDNet Direct email newsletter.

Read more in this forum topic or make sure you're signed up (from the right-hand sidebar on the homepage) and read Thursday's newsletter to get in the running!


Member Since 05 Jan 2013
Offline Last Active Feb 02 2013 09:09 AM

Topics I've Started

Help needed setting up camera transform

05 January 2013 - 03:13 PM

First time poster here.  I tried searching the forum for prior posts related to this, but didn't find exactly what I needed. 


I am trying to make a simple 3d rendering engine just to demonstrate to myself that I understand the math.  I have not taken linear algebra, but have spent some time trying to self-teach with online and textbook tutorials and have a working understanding (I think).  I am writing this simple engine with lazarus free pascal.  


I have found several tutorials that I have tried reading through.  Most recently from www.scratchapixel.com.


First I have objects that are positioned in the world with a world transform/matrix.


Next I am trying to set up my camera transform.  But I am apparently doing something wrong.  I am hoping that if I write out my understanding here, someone can pick up where I am off.


First, I am planning on using a right-handed matrix and math.  I think this means that when I consider the axis at (0,0,0), +X will go to the "right", +Y will go "up", and +Z will come "out towards me".


Next, I think that to create the camera transform, one has to create cardinal vectors for the new coordinate space: In, Up, and Left.


In = LookingAtPosition - Camera Position

Left = In X (0,1,0)  (in vector cross a global up vector)

Up = in X Left 


Next, I think that the parts of a matrix are as follows.  But I am uncertain about this.


[Left.x,   Left.z,  Left.z,  A   ]

[  Up.x,    Up.y,   Up.z,   B  ]

[   In.x,      In.x,    In.z,   C   ]

[       0,          0,        0,     1 ]


A,B,C as a column vector is the position of the camera. (e.g. A=T.x, B=T.y, C=T.z)


I have some output from the engine, but this web page interface won't let me paste the text in. (I assume this is a defense against spammers).


Before I go any further, can anyone comment on my understanding so far?


Any help appreciated.


Kevin T